The Copernican Period in the lunar geologic timescale runs from approximately 1.1 billion years ago to the present day. The base of the Copernican period is defined by impact craters that possess bright optically immature ray systems. The crater Copernicus is a prominent example of rayed crater, but it does not mark the base of the Copernican period. No mare basalts are known to have erupted within the Copernican period, and for this reason, the Moon's internal geologic activity is thought to have effectively ceased by this time.
Read more about Copernican Period: Definition, Relationship To Earth's Geologic Time Scale
Famous quotes containing the word period:
“Unless your baby becomes uncomfortable and tries to push away, don’t worry that you’re cuddling too much. That way, when she reaches adolescence and goes through a normal period of being terribly embarrassed even to be seen with you in public, you’ll have some memories to tide you over until she comes around again.”
—Lawrence Kutner (20th century)